A conventional stool flush control device 80, as shown in FIGS. 14 and 15, mounted to the bottom inside the water reservoir tank of the stool, comprises a main pipe 81, a stopper body 82, and a lock ring 83, wherein a screw-thread section 811 disposed on the outer periphery of the lower section of the main pipe 81, a longitudinally penetrating flow passage 812 disposed in the interior of the main pipe 81, an upward extending manifold 813 connected on one side near the top of the main pipe, the manifold 813 being through with the flow passage 12, the stopper 82 covering the top of the flow passage 812, and through a connecting bar 821 pivotably connected to the lower section of the manifold 813, the lock ring 83 having inner screw-threads, the lower section of the main pipe 81 downward passing through from the bottom of the water reservoir tank, by means of the lock ring 83 threw-coupled to the screw-thread section 811 and hooking up the outer bottom of the water reservoir tank, the flush control device 80 fixedly disposed inside the water reservoir tank. The actuation principle of above-mentioned conventional flush control device 80 is: when the stopper 82 is pulled up, the flow passage 812 is opened, and the water will flow out. However, the conventional flush control device 80 has two disadvantages: a) the water outflow of the flow passage 812 cannot be controlled. It causes a waste; b) if any of the components of the flush control device 80 is damaged, and needs replacement, it is less convenient for dismounting or mounting because the lock ring lockably hoops up the outer bottom of the water reservoir tank.
Another conventional stool flush control device 90, as shown in FIGS. 16 and 17, comprising: one main pipe 91, one valve assembly 92 and one lock ring 94, wherein the top of the main pipe 91 integrally extending to form a connecting ring 911, a screw-thread section 912 disposed on the outer periphery of the lower section of the main pipe 91, the main pipe 91 having an inlet 913; a control device disposed in the valve assembly 92 and controlling the valve-controlling member 93 on vertical movement so as to close or open the inlet 913, a plurality of the raised portions 921 disposed on the outer periphery of the lower section of the valve assembly 92, the raised portions 921 inlaid in the L-shaped tank 914 of the inner wall of the connecting ring 911 so that the valve assembly 92 being through with the main pipe 91; the lock ring 94 having inner threads, two washers 95 and 96, sleeved over the main pipe 91, the lower section of the main pipe 91 downward passing through from the water reservoir tank, by means of the lock ring 94, screw-coupled to the screw-thread section 912 of the main pipe 91, and hooking up the outer bottom of the water reservoir tank so that the flush control device 90 fixedly disposed inside the water reservoir tank. The above-mentioned conventional flush control device 90 can control the water outflow by means of the distance and the duration which the valve member 93 travels so as to achieve water saving. The easily damaged components inside the valve assembly and the damaged valve can be easily maintained by replacing the valve assembly. However, this conventional flush control device 90 is not interchangeable with above mentioned first conventional flush control device 80. If the user who uses the first conventional flush control device wants to replace with the second flush control device 90, he has to dismount the whole flush control device 80, and buy a complete set of flush control device 90 because the second conventional flush control device cannot fit the components of the first conventional flush control device. It causes an unnecessary waste.